Btrfs: fix balancing oops when invalidate_inode_pages2 returns EBUSY

invalidate_inode_pages2_range may return -EBUSY occasionally
which results Oops. This patch fixes the issue by moving
invalidate_inode_pages2_range into a loop and keeping calling
it until the return value is not -EBUSY.

The EBUSY return is temporary, and can happen when the btrfs release page
function is unable to release a page because the EXTENT_LOCK
bit is set.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index e71264d1c2c9..c04f7f212602 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -2553,8 +2553,13 @@ int relocate_inode_pages(struct inode *inode, u64 start, u64 len)
         last_index = (start + len - 1) >> PAGE_CACHE_SHIFT;
 
         /* make sure the dirty trick played by the caller work */
-        ret = invalidate_inode_pages2_range(inode->i_mapping,
-                                            first_index, last_index);
+        while (1) {
+                ret = invalidate_inode_pages2_range(inode->i_mapping,
+                                                    first_index, last_index);
+                if (ret != -EBUSY)
+                        break;
+                schedule_timeout(HZ/10);
+        }
         if (ret)
                 goto out_unlock;